An emulsion of ethiodized oil was tested in normal and carcinogen induced hepatoma bearing monkeys. At a dose of 0.2 mg/Kg (one tenth the previously used dose) there was an average increase of 23 EMI units in the opacity of the liver. Opacification of spleen was even better. The visualization of tumors and small lesions in the monkey with hepatoma was significantly improved. Clinical trials have been initiated and the results are being presently evaluated.